Furnace and the operation thereof for industrial purposes



Nov. v8, 1938. H. w. SPENCER ET AL FURNACE lAND rI-I'IE OPERATIONTHEREOF FOR INDUSTRIAL PURPOSES Filed oct. s, 1935 a sheets-sheet 1 Fly.

FUHNACE AND THE OPERATION THEREOF FO`R INDUSTRIAL PURPOSES Filed oct. 8.1935 3 sheetsl-sneet 2 Nov. 8, 1938. H. w. SPENCER ET A. 2,135,645

FURNACE AND THE OPERATION THEREOF FOR INDUSTRIAL PURPOSES Filed Oc-t. 8,1935 5 Sheets-Sheet 3 Patented Nov. 8, 1938 UNm-:D 'STATES 4FURNACE ANDTHE OPERATION 'manner FOR INDUSTRIAL PURPOSES Henry Wilmot Spencer,Roehampton Lane, lilon-I I don, and Leonard Sherrington Davis, BexleyHeath, England, assignors Corporation, Detroit,

Michigan Application October 8,

to Bigelow-Lptak Mich., a corporation of 1935, Serial No. 44,097

In Great Britain October 9, 1934 5 Claims.

This invention relates to furnaces for industrial purposes other thantunnel kilns for clay products and more particularly to furnaces fortreating' pansion and contraction under heating and cooling conditions,while they are costly in upkeep and wasteful in operation.

' The inherent factors of this older type of construction impose certaincharacteristics on the furnace irrespective of the particular purpose or20 duty for whichl it is designed. For example, a

furnace cannot readily be designed to suit a definite heating time orcooling time, o1; to afford a definite -time to change from onetemperature to another. Furthermore, the distribution of 25 heat, or therate of heating throughout the furnace, can only be controlled in-arough and ready manner. If a furnaceV be designed to keep its Iradiation losses to a minimum, then due to the heavy construction (ifthe furnace is not usedv 30 continuously) its losses in the heat storedin its Walls and arch are considerable. Conversely, if it be attemptedto reducethe heat storage losses then radiation losses becomeproportionately greater. Due to the mechanical strain involved 35 in therefractoriesof the construction and the high degree of soaking oftenobtained, the life of the refractories is reduced and when repairs andreplacements are necessary they are diilicult to effect.

40 V Accordingly an object of the present invention is to obviate thesedefects or to reduce 'them to a minimum by providing a construction offurnace vwhich affords not only economy in avoidance of heat losses, andin time taken in heating up a 45 furnace or in cooling after use, butenable the temperature conditions of the furnace to be controlled insuch a way as to give flexibility of treatmeht whilst possessing thecapacity to maintain any required constant temperature treatment as 50may be predetermined..

An aim of the invention is to secure the advantages of the suspendedarch (with or without associated suspended wall construction) which hashitherto been employed for steam generator work, 'in the field ofindustrial furnaces as indicated.

structure has Ibeen very thick and to adapt this character ofconstruction to afford improved furnace operation and efllciency inaddition to the advantages of replacement and repair inherent in thistype of construction.

It is to be understood that by the term suspended arch a single orrelatively thin (as compared with nonsuspended structures) layer ofrefractory blocks hung from a super-structure by the aid of hooks orlink members.

Similarly, by the phrase suspended wall is meant a wall the blocks (o rmain blocks, irrespective of filler blocks) of which are hung upon hooksor brackets carried by a rear framework so that the lower blocks do notsustain the cumulative weight of those above. 'I'he suspended roof typeof construction is exemplified in British patent specifications Nos. forsteam generators, while the suspended wall is similarly exemplified inBritish patent specifications Nos. 310,305 and 385,717.

According to the invention an industrial furnace of the kind describedis provided with' a suspended refractory arch enclosed in an outerinsulating housing between which and the arch variable quantities of airare mechanically circulated and utilized for furnace combustionpurposes,Y in order to aid in controlling the temperature conditions orworking of the furnace.

The invention also consists in an industrial furnace of the kinddescribed comprising a susis meant a roof or arch comprising 215,464 and297,271

pended refractory arch, or a suspended arch vand suspended refractorywalls, enclosed in an insulating `housing affording an air jacket, andregulatable mechanical means adapted to circulate air through the jacketover the arch (or arch and walls) to aid in controlling the temperatureconditions of the furnace and having means for utilizing heated air fromthe jacket for combustion purposes in the furnace.

According to a further feature of the invention means is provided fordiverting heated air to permit its utilization for other purposes whendesired. i y/ It is, of course, well known in the older types offurnaces above referred to, to allow air to circulate around the wallsor roof or arch of such furnaces and to utilize such air for combustionpurposes either directly or by passage to an air heater. In such cases,however, owing to the massive construction and great heat storagecapacity, the heat absorbed by the air was relatively slight and anyheat transfer between the air and walls was useless for influencingfurnace conditions and y could not be employed asa controlling factorin` the furnace operation.

4It has also beenproposed in tunnel kilns for clay ware to provide asuspended refractory arch and to circulate air mechanicallyv through thespace between the arch and an enclosing outer casing, the heated airbeing then introduced into the wate'r smoking zone of the tunnel.

It has also been proposed in steam generator furnaces to ,provide ductsor passages between an inner suspended wall and an outer masonry wallthrough which air is drawn by the furnace draught for preventing theoverheating of the.

refractories of the suspended wall and for combustion purposes.

A furnace arch construction has also been proposed comprising transversebars or girders upon which the arch bricks are threaded, a small spacebeing left between the underside of each girder and the bricks threadedthereon through which air may be passed for cooling the bars and thenled to the furnace.

In the accompanying drawings:-

Figure 1 is a side sectional elevation illustrating the inventionapplied to a gas or oil fired furnace typical of many furnaces `used fora variety of purposes such as billet, bar, or sheet heating or forannealing.

Figure 2 shows cross sections of the furnace seen in Figure 1, the lefthalf being taken dn the line A--A and the right half on the line B-B ofthe figure looking towards the burners.

Figure 3 is a side sectional elevation of an oil or gas fired billetheating furnace illustrating an application of the invention thereto.

Figure 4 is a cross sectional view taken on the line C-C of Figure 3.

Figure 5 is azfragmentary elevation partly in section illustrating theinvention applied to a muiiie furnace.

Figure 6 is a transverse section according tov Figure 5 on'the line d, dand Figure 'l is a fragmentary sectional plan taken on the line e, e ofFigure 6.

In carrying the invention into eiect with reference to Figures 1 and 2,a metal framework comprising uprights and horizontal girders Iy whichare enclosed by suitable insulation or lagging wall 2, is adapted toform the housing for the furnace proper. Within this housing suspendedwalls 3 for the sides and front and rear of the furnace are erected.These walls comprise refractory blocks 3a hung on metal brackets` orangle bars 3b,\intermediate filler bricks 3c being vusually employedbetween the blocks after the known mode of the,construction of suspendedwalls. The suspended arch 4 comprises a series of recessed blocks 4a therecesses of f which receive transverse bars which are carried by hookmembers 5 indicated by the dotted lines which are in) turn hung upontransverse rods 6 supported by the longitudinal girdersv I. While exam'-ples of the hook members and fittings in the recesses of the arch blocksare shown in Figure6 it will be understood that any suitable form' ofsuspended block and suspension means may be employed and such may bevaried to suit the character or design of furnace.

The suspended wall and arch construction is arranged to afford inconjunction with the spaced housing walls and roof 2, an air jacket A.Any

suitable form of heat source or fire may be utilized. In the presentinstance oil or gas fired burners 'I are illustrated and the hearth maybe of any'desired construction according to the particular purpose forwhich the furnace is intended. The air jackets at the front and rearwalls may be in communication with one another through passages 8beneath the hearth and the roof jacket has free communication with thewall jackets. `'I'he oil or gas burners have air inlets in communicationwith the front jacket so that air may be supplied therefrom into theburners for combustion purposes. At the front of the vfurnace or in anyother suitable position, a conduit 9 is provided for the introduction ofair for circulation through the air jacket A. 'Ihis conduit is connectedto the delivery of a centrifugal or other blower or fan I0 driven by avariable speed prime mover, such as a variable speed electric motor, orthrough variable speed vgearing vso that the rate of circulation may beregulated.

A conduit 2a is provided for diverting air from the jacket when desiredand may be provided with a damper or valve for controlling the quantitythus diverted. It will be understood that such control of the divertedair in conjunction with the variable speed fan enables .gthe quantity ofair admitted to the burners to be regulated.

Alternatively the quantity of air circulated may be regulated by dampersor valves arranged in the delivery conduit to the jacket or elsewhere.

In Figures 3 and 4 the invention is seen as applied to a continuousbillet reheating furnace, the hearth and burners of which may be of anyusual construction. The-'walls II may be of the usual built-upconstruction and are formed with recesses to receive the outermost rowof blocks of the suspended arch 4, the blocks 4a of which are hung(after the manner described in refer-` ence to Figure 1) from rodssupported by transverse girders I of a framework or housing enclosed byinsulating slabs or lagging and anfording an air jacket A over the roofor arch of the furnace. 'Ihe burner 'I is supplied with combustion airthrough a conduit 1a from the roof air jacket A of the furnace. 'I'heair is circulated ,through the jacket from the fan I0 and conduit 9 asdescribed in reference to Figure 1.

In applying the invention to a muille furnace as illustrated in Figures5, 6 and '7, the suspended walls and arch are constructed after themanner already described, the walls comprising blocks` 3a carried onangle brackets 3b whilst the recesses of blocks 4 of the roof areengaged by longitudinal bars` 4b slung on hooks 4c. The upper ends ofthe hook members 4c are hung upon longitudinal rods 6 supported upontransverse girders I. The suspended arch and walls are enclosed byinsulation slabs or lagging 2 and provide the air jacket A, the jacketbeing supplied with circulating air through the conduit 9 from the fanIIJ. 'I'he burners I of the mutue furnace receive air from the jacketithrough the branches 1a. The mulile of the furnace is indicated at I2and may be of any suitable construction, being locatedin spacedrelaltionship with the suspended walls) and suspended arch 4. The spacebetween the muille tiles and the walls is preferably provided withlspacing or positioning ribs or partitions I2a.

provided with bailles for directing .the course'of aisaeas the aircurrents for example transverse baffles extending alternately from eachside of the arch jacket towards the other side may be provided to givethe air a zigzag or serpentine course.

In operation, it will be appreciated that in all yfurnaces according tothe invention the air circulated by the fan travels in heat transferencerelationship with the backs of the suspended blocks and is available forcombustion purposes. The suspended arches are relatively thin ascompared with non-suspended structures and have relatively small heatstorage capacity, and because of this the circulation of the air' iscapable of influencing the temperature conditions and the temperature inthe furnace, within certain ranges, will rise and fall according to therate of circulation of the air. As the rate of circulation of the air iscontrollable the temperature lconditions in the furnace `cancorrespondingly be controlled. Owing to the nature of the suspended archuseful heat transference is effected such that on' the one hand thebacks of the blocks may be maintained at a. suitably low temperaturewhile on the other hand the air takes up practically all the heat lostthereby, such heat units being used regenratively in the furnace, forexample througn the medium of the burners. In addition to providingmeans for utilizing the heated air from the jackets for combustionpurposes, arrangements are also made for diverting air from the jacketsand the amount of air thus diverted may be controlled in any convenientway. It will thus be seen that the invention provides means forcontrolling the amount of air circulated through the jackets and theamount admitted to the furnace for combustion purposesl and by suitableregulation of these quantities the temperature conditions within thefurnace may be controlled within the desired limits. Air which isdiverted and not -used for combustion purposes in the furnace may beutilized for some other purpose where heat is required as for example inconnection with another furnace either for combustion purposes or forheating up.

Also when a furnace is to be stopped or put out of commission thecirculation of air is effective for rapidly cooling the furnace whilethe heated air derived during this period may be utilized in anotherfurnace, either for combustion purposes or for heating up or other uses,for example for drying fuel where pulverized fuel is employed.

It is to be understood that the invention is not limited in any way tothe particular examples of furnaces described and illustrated herein andthat the design and arrangement of the suspended arch or arch and wallsand the housing may be varied to provide air jacketing means as may berequired to suit the particular conditions and uses of the furnace orits association with another furnace or battery of furnaces. Ruthermore,although the invention has been illustrated with reference to oil or gasburners, other fuels may be employed in ring with the necessarymodication in hearth construction or design.

Having now described our invention, what we claim as' new and desire tosecure by Letters Patent is:-

1. The method of controlling the temperature conditions or working of anindustrial furnace of the kind described, which consists in mechanicallycirculating a variable quantity of air between a suspended refractoryarch of the furnace treatment chamber and an enclosing insulatinghousing, utilizing air thus circulated for combustion purposes in thefurnace and separately controlling the quantity of air circulated andthe quantity of heated air admitted to the furnace for combustionpurposes.

2. The method of controlling the temperature conditions or working of anindustrial furnace of the kind described which consists in mechanicallycirculating air between a suspended refractory arch of the furnacetreatment chamber and an inclosing housing in quantity sufficient toobtain the desired control by withdrawal of heat from the arch, andadmitting part of the air thus circulated to the furnace for combustionpurposes.

3. In an industrial furnace of the kind described a suspended refractoryarch and a Suspended refractory wall for the treatment chamber, anenclosing housing forming an air jacket for the arch and wall,regulatable mechanical means for circulating air through the jacket ofthe arch and wall in quantity sufficient to control the temperatureconditions in said chamber, and mea-ns for admitting a proportion of airfrom the jacket for combustion purposes in the furnace.

4. In an industrial furnace of the kind described a suspended refractoryarch and a suspended refractory wall for the treatment chamber, anenclosing housing forming an air jacket for the arch and Wall,regulatable mechanical means for circulating air through the jacket ofthe arch and wall in quantity suicient to control the temperatureconditions in said chamber,l means for utilizing heated air from thejacket for combustion purposes in the furnace, and means for divertingheated air from the jacket.

5. In an industrial furnace of the kind described a suspended refractoryarch and a suspended refractory wall for the treatment chamber, anenclosing housing forming an air jacket for the arch and wall.regulatable mechanical means for circulating air through the jacket ofthe arch and wall in quantity suilicient to control the temperatureconditions in said chamber, means for admitting heated air from thejacketto the furnace for combustion purposes, means for diverting airfrom the jacket and means for regulating the quantity of air divertedwhereby the temperature or working conditions of the furnace may becontrolled.

HENRY WILMOT SPENCER. LEONARD SHERRINGTON DAVIS.

